The present invention relates to a turbocharger equipped with a wastegate.
Japanese Laid-Open Patent Publication No. 2014-005789 discloses a turbocharger equipped with a wastegate. In the turbocharger, with the valve member of the wastegate placed at the position for closing the wastegate port, a shaft is inserted through the insertion hole of the valve member to join the valve member and the shaft to each other. This eliminates the misalignment between the wastegate port and the valve member due to the dimensional tolerances of the wastegate port or the wastegate.
There is a gap between the shaft and the bushing pivotally supporting the shaft. Thus, even if the valve member and the shaft are joined together with the wastegate port closed, inclination of the shaft in the bushing may create a gap in the sealing portion of the wastegate, that is, between the valve member and seating surface, which contacts the valve member.
Such a gap would leak exhaust gas therethrough even if the wastegate port is closed in the wastegate, which reduces the efficiency of the forced induction.
In addition, when the seating surface or the portion of the valve member that contacts the seating surface is scratched, a gap may be created in the sealing portion. Thus, such a problem is not limited to turbochargers that have a wastegate, in which the shaft and the valve member are joined with the wastegate port closed as described above, but also applies to any turbocharger including a wastegate.